Work vehicles are provided with a torque converter for transmitting power from a power source such as an engine and the like to a transmission input shaft. A torque converter generally has a torque converter body that transmits the power through a liquid, and a lock-up clutch device. The lock-up clutch device mainly includes a piston that operates by hydraulic pressure, and a clutch unit that switches between on (power transmission) and off (power transmission disconnection) due to the operation of the piston. When the vehicle speed reaches or exceeds a certain speed, the clutch unit of the lock-up clutch device then switches on, and the power from the engine is transmitted directly through the lock-up clutch device to the transmission input shaft without going through the torque converter body.
A hydraulic pump is required in this type of torque converter for supplying operating fluid to the torque converter body or to the piston in the lock-up clutch device. The hydraulic pump is most commonly arranged, for example, eccentrically from an extended shaft of the input shaft in a transmission case.
With this type of hydraulic pump disposition however, a gear mechanism for producing the rotation in the pump drive shaft from the input shaft is required in addition to a pump drive shaft for driving the hydraulic pump. Thus, the width of the entire device is increased and the number of parts that constitute the gear mechanism is also increased. Accordingly, as discussed in Japanese National Publication of International Patent Application No. 2006-521513, a configuration in which a hydraulic pump and a drive shaft of the hydraulic pump coaxial to the torque converter rotary shaft are disposed has been proposed.